1. Field of the Invention
The present invention relates to a method for producing polymer particles.
2. Description of the Related Art
Polymer particles are produced by various polymerization methods such as suspension polymerization, emulsion polymerization, and precipitation polymerization. Among these polymerization methods, suspension polymerization is industrially widely used as, for example, a method for producing a polymerized toner because a functional substance such as a coloring material can be easily included in polymer particles.
Recently, the area of study regarding a technique for controlling the molecular weight of polymer particles has been activated. For example, a method has been reported in which living radical polymerization such as atom transfer radical polymerization or reversible addition-fragmentation chain transfer polymerization is combined with suspension polymerization (Adam Limer, Alex Heming, Ian Shirley, and David Haddleton, European Polymer Journal, 2005, Vol. 41, pp. 805-816 (Non-Patent Literature 1), and John D. Biasutti, Thomas P. Davis, Frank P. Lucien, and Johan P. A. Heuts, Journal of Polymer Science: Part A: Polymer Chemistry, 2005, Vol. 43, pp. 2001-2012 (Non-Patent Literature 2)). However, from the standpoint of problems of, for example, a remaining catalyst, safety and sanitation, and the cost, at present, it is difficult to industrially use many of such living radical polymerization methods.
A method in which a polymerization control agent such as a chain transfer agent or a polymerization inhibitor is used is known as a method for industrially controlling the molecular weight of polymer particles. However, a significant difference in the molecular weight may be caused or the polymerization conversion rate may be significantly decreased depending on a slight difference in the amount of polymerization control agent used (Japanese Patent No. 3332721 (corresponding U.S. Pat. No. 5,750,303) (Patent Literature 1) and Japanese Patent Laid-Open No. 2006-221203 (no corresponding foreign application) (Patent Literature 2)). Although the molecular weight can also be controlled by changing the amount of polymerization initiator or the polymerization temperature, such a method has many problems in terms of the cost and safety for the purpose of obtaining polymer particles having a low molecular weight, for example.
As a method capable of easily controlling the molecular weight at a low cost, Patrick Lacroix-Desmazes, Romain Severac, and Bernard Boutevin, Macromolecules, 2005, Vol. 38, pp. 6299-6309 (Non-Patent Literature 3) discloses reverse iodine transfer polymerization.
Furthermore, Jeff Tonner, Patrick Lacroix-Desmazes, and Bernard Boutevin, Macromolecules, 2007, Vol. 40, pp. 186-190 (Non-Patent Literature 4) discloses that, in a process of producing polymer particles, the process being performed by using suspension polymerization and reverse iodine transfer polymerization in combination, satisfactory molecular-weight controllability and a satisfactory polymerization conversion rate can be achieved by adding hydrogen peroxide and hydrochloric acid to an aqueous phase.